Methods for interference detection between laser head and part,and correction of laser head posture were proposed. The stero lithography (STL) model of laser heads was built and divided into two types of concave and convex. The interference areas were found out by using the ubiety of the disperse points on STL model and normal vector of triangles that are composed of laser head model. A method to avoid the interference by rotating the laser head and to calculate critical rotating angle by using a series of cutting planes cutting the laser head model was presented. The algorithms were implemented by using VC++ and OpenGL. The case studies show that the method can primely detect the interference areas of laser head and part,and correct the posture of laser head so as to avoid the interference. The whole process of detection and correction are stable and reliable.